DNA traces on clothes of drowned bodies can provide important evidence for police investigations, especially in cases of suspected suicides or homicides. However, it is generally assumed that the water "erodes" a large part of the DNA depending especially on the exposure time. In forensic casework, DNA of suspects could be found frequently on clothes of drowned bodies after hours, sometimes days of exposure to water. This study was conducted to attempt a general statement about the conditions under which sufficient DNA remains can be expected for molecular genetic analysis. For this purpose, different scenarios were designed including DNA from three to five people, different types of waters (tap, pond, bathtub and river) for various time periods, with higher water pressure, different temperature, and soapy water (bathtub). Epithelial cells and blood cells were mounted on cotton cloths, and the DNA left after exposure was analyzed using the Powerplex® ESX17fast kit. In the indoor experiments, complete profiles could be seen even after 10 min rinsing of clothes under the tap and after 1 week in the bathtub. Outdoors, the results differed considerably between summer and winter as well as between pond and river. The longest exposure time still resulting in a complete profile was 2 weeks for a sample with skin cells in the pond during winter. In summer, the time period for erasing the bulk of DNA was 4 hours regarding epithelial samples and more than 1 day for blood samples in pond and river environments. All in all, the results demonstrate that DNA could still be recovered from clothes exposed to water for more than 1 week.

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The transfer of DNA directly from one item to another has been shown in many studies with elaborate discussions on the nature of the DNA donor as well as material and surface of the items or surrounding features. Every DNA transfer scenario one can imagine seems to be possible. This evokes more and more intricate scenarios proposed by lawyers or attorneys searching for an explanation of the DNA of a certain person on a distinct item with impact on a crime. At court, the forensic genetic scientist has to comment on the probability of these scenarios thus calling for extensive studies on such settings. Here, the possibility of an involvement of a second person as a carrier of the donor's DNA in a variety of different scenarios including three pairs of people and two kinds of items (textiles and plastic bags) was investigated. All transfer settings were executed with and without gloves on the carrier's hands. DNA left on the items was isolated and analyzed using the Powerplex® ESX17 kit. In 21 out of 180 samples, all alleles of the donor DNA could be obtained on the second item (12%), on eight samples, the donor's DNA was dominant compared to all other alleles (38% of samples with complete donor profile). Additionally, 51 samples displayed at least more than half of the donor's alleles (28%). The complete DNA profile of the carrier was found in 47 out of 180 samples (42 partial profiles). In summary, it could be shown that a transfer of donor DNA from epithelial cells through a carrier to a second item is possible, even if the carrier does not wear gloves.

The detection of DNA of a certain person on the inside of a piece of clothing involved in a crime scene is usually seen as confirmation that this person is the owner or bearer and therefore participated in this crime. However, besides the possibilities of secondary or even tertiary transfer of DNA, the accused often argues that he lent the garment to another person who by chance did not leave any DNA while committing the crime. Then, forensic genetic scientists have to answer the question how long DNA persists on an item used in daily routine and how long a piece of clothing must be worn to definitively leave detectable DNA behind. In an attempt to answer these questions, several scenarios with two or three individuals wearing the same sweatband for different time periods were set up. DNA left on the sweatbands was isolated, quantified, and then analyzed using the Powerplex® ESX17fast kit. The majority of samples displayed all alleles of both/all three wearers on the outside (67%) as well as on the inside (80%) of the sweatbands. In contrast, a single profile of the first wearer could only be found once among all 204 samples, a single profile of the second wearer in 7% of samples. Wearing the sweatband for only 10 min was enough to result in a complete profile of the second wearer in 79% of samples. So, it is highly unlikely to wear/use a piece of clothing for even a short period of time without leaving own DNA behind.

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